/* Copyright (c) 2018 PaddlePaddle Authors. All Rights Reserved.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
 
 http://www.apache.org/licenses/LICENSE-2.0
 
 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License. */

#include <metal_stdlib>
using namespace metal;

struct NearestInterpParam {
    float ratio_h;
    float ratio_w;
    float align_delta;
};

kernel void nearest_interp(texture2d_array<float, access::sample> inTexture [[texture(0)]],
                  texture2d_array<float, access::write> outTexture [[texture(1)]],
                  constant NearestInterpParam &param [[buffer(0)]],
                  uint3 gid [[thread_position_in_grid]]) {
    if (gid.x >= outTexture.get_width() ||
        gid.y >= outTexture.get_height() ||
        gid.z >= outTexture.get_array_size()) return;
    float ratio_h = param.ratio_h;
    float ratio_w = param.ratio_w;
    // 如果使用中心对齐，align_delta=0.5，否则为-1，在CPU中计算后传入
    float align_delta = param.align_delta;
    
    uint x = gid.x * ratio_w + align_delta;
    uint y = gid.y * ratio_h + align_delta;
    float4 input = inTexture.read(uint2(x, y), gid.z);
    outTexture.write(input, gid.xy, gid.z);
}

kernel void nearest_interp_half(texture2d_array<half, access::sample> inTexture [[texture(0)]],
                                texture2d_array<half, access::write> outTexture [[texture(1)]],
                                constant NearestInterpParam &param [[buffer(0)]],
                                uint3 gid [[thread_position_in_grid]]) {
    if (gid.x >= outTexture.get_width() ||
        gid.y >= outTexture.get_height() ||
        gid.z >= outTexture.get_array_size()) return;
    half ratio_h = param.ratio_h;
    half ratio_w = param.ratio_w;
    // 如果使用中心对齐，align_delta=0.5，否则为-1，在CPU中计算后传入
    half align_delta = param.align_delta;
    
    uint x = gid.x * ratio_w + align_delta;
    uint y = gid.y * ratio_h + align_delta;
    half4 input = inTexture.read(uint2(x, y), gid.z);
    outTexture.write(input, gid.xy, gid.z);
}
